About half of JJB Sports's 180 stores are likely to close with the loss of around 2,000 jobs if rival Sports Direct International concludes a deal to take over the struggling retailer this week.

The bid from Mike Ashley, owner of Newcastle United Football Club and founder of Sports Direct, is the leading contender of the eight tabled. He is believed to have plans to axe all but the most profitable stores with the rest of the company being put into administration.

Competition authorities are likely to scrutinise any deal, as Sports Direct is already Britain's largest high-street sporting goods chain.

In April, a £30m strategic investment by shareholders and Dick's Sporting Goods of America – another potential buyer – was announced to try to turn the company's fortunes around. But by July, months of poor weather and dashed hopes pinned on Euro 2012 replica kit led sales to tumble further amid growing debts.

Shareholders have been warned that all their stakes are likely to be wiped out under any deal. JJB is working towards a "pre-pack" arrangement that allows it to be placed into administration and sold immediately, allowing buyers to jettison lossmaking stores.

Former owner Dave Whelan, the chairman of Wigan Athletic FC, indicated recently he may step in to save jobs, although he has ruled out trying to revive the brand.